RU2764972C2 - Pump rod column, coupling for pump rod column and method for extracting fluid from well, and pump system - Google Patents

Abstract

FIELD: hydrocarbon production.SUBSTANCE: pump rod column contains: a pump rod having an end containing a rod with external thread, a valve rod sleeve and a coupling. The sleeve of the valve rod has the first end containing a rod with external thread, and the second end containing a threaded part with internal thread, wherein the sleeve of the valve rod is connected to a downhole pump. The coupling contains a core having the first end, a central section and the second end, wherein each of the first end and the second end has an end face, wherein the first end linearly tapers inwards from the central section to the first end face. A diameter of the first end surface is smaller than a diameter of the second end surface. The coupling is made of a spinodal hardened copper-nickel-tin alloy, which has a sliding friction coefficient from 0.175±10% to less than 0.4 when measured on carbon steel, wherein a threaded hole passes through the entire core from the first end to the second end. The threaded hole at the first end of the coupling is a response to external thread of the valve rod sleeve, and the threaded hole at the second end of the coupling is a response to external thread of the pump rod.EFFECT: provision of increased internal abrasion resistance.20 cl, 3 tbl, 9 dwg, 3 ex

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No. 62/473,792, filed March 20, 2017, the contents of which are incorporated herein by reference in their entirety.

PRIOR ART

The present invention relates to couplings made from spindally hardened copper alloy. Couplings are especially useful for connecting sucker rod components to a downhole pump. The alloys preferably have a sliding friction coefficient of less than 0.4 when measured against carbon steel.

Hydrocarbon recovery devices typically include a downhole pump for extracting hydrocarbons from an underground reservoir, a power source to power the pump, and a sucker rod lifting system connecting the power source and the downhole pump. The sucker rod lifting system comprises a plurality of sucker rods connected to each other by couplings. The rods and couplings are connected by means of a nipple threaded connection. Also, when connecting the sucker rod lifting system to the downhole pump, additional couplings with threaded connections are used. Damage to threaded connections due to abrasion (wear associated with adhesion between sliding surfaces) can adversely affect the mechanical integrity of the connection and lead to a break in the connection between the power source and the pump. In addition, the hydrocarbon recovery system operates inside the pipeline. Damage to the pipeline and coupling resulting from repeated contact between the outer surface of the couplings/pump and the inner surface of the pipeline can adversely affect the mechanical integrity of the pipeline or coupling, resulting either in the leakage of hydrocarbons carried by the pipeline to the environment, or in the separation of the coupling connection from the pump string rods. Any of these events will actually halt the download process and often result in very costly extra steps to fix such problems.

The required characteristics of couplings used in such systems include high tensile strength, high fatigue strength, high fracture toughness, abrasion resistance and corrosion resistance. Conventional couplings are typically made from steel or nickel alloys, which do not offer the full range of desirable internal characteristics, such as abrasion resistance. To increase wear resistance, expensive surface treatments of couplings made of steel or nickel alloys, as well as the inner surface of the pipeline in which the coupling is located, are usually applied. This surface treatment wears off over time and must be reapplied periodically during the life of the parts to maintain their effectiveness. In addition, while coatings can reduce wear on the component to which they are applied, such coatings are often incompatible with other system components that the coating may come into contact with.

Thus, it is required to develop new couplings having increased internal abrasion resistance, as well as other required properties, which will ensure the compatibility of the materials of the coupling and pipeline; which means that both of them will be subject to minimal wear during operation, will not require any protective coatings and will reduce the overall hydraulic losses of the pumping system.

DISCLOSURE OF THE INVENTION

The present invention relates to couplings made from spinodally hardened copper alloys, and more specifically, to a coupling inserted between a sucker rod of a sucker rod string and a downhole pump valve rod bushing. Couplings can be considered as part of the sucker rod string. The couplings have a unique combination of properties, including high tensile strength, high fatigue strength, high fracture toughness, abrasion resistance and corrosion resistance. This combination of properties limits the occurrence of destructive damage to couplings and other components in pumping systems using such couplings (eg, sucker rods and pipelines), while maintaining mechanical functionality during hydrocarbon production operations. The useful life of such components is also increased, with a significant reduction in the cost of equipment used to recover hydrocarbons.

In various embodiments of the present invention, couplings for a sucker rod string are disclosed, comprising a core having a first end, a central portion, and a second end. Each of the first end and the second end has an end surface. The first end has a linearly tapered part extending from the central section inward and ending at the first end surface. In other words, the first end surface has a smaller diameter than the central portion. The second end surface of the second end has a rounded edge. Couplings are made of spinodally hardened copper-nickel-tin alloy, which has reduced friction and increased wear resistance.

The diameter of the first end surface may be less than the diameter of the second end surface. In some specific embodiments, a threaded hole extends through the entire core from the first end to the second end. The hole threads may have a Rockwell C hardness (HRC) of about 20 to about 40.

The threaded hole at the first end may be configured to connect to a valve stem bushing that may be connected to a downhole pump. The first end surface may abut a shoulder of the valve stem bushing. The outer diameter of the coupling may be larger than the outer diameter of the valve stem bushing.

The threaded hole at the second end may be configured to be connected to the sucker rod of the sucker rod string. The second end face may abut the sucker rod shoulder. The outer diameter of the coupling may be larger than the outer diameter of the pump rod.

In addition, the present invention discloses sucker rod strings comprising a sucker rod having an end containing an externally threaded rod and a valve rod bushing having an end containing an externally threaded rod. A clutch is also provided as above. The threaded hole at the first end of the coupling is mate with the external thread of the valve rod bushing, and the threaded hole at the second end of the coupling is mate with the external thread of the pump rod. The sleeve contains a spinodally hardened copper-nickel-tin alloy.

Also disclosed in the present invention are pumping systems comprising a downhole pump, a power source for powering the downhole pump, and a sucker rod string positioned between the downhole pump and the power source. The pump rod string comprises a pump rod having an end containing a rod having an external thread and a valve rod bushing having an end containing a rod with an external thread. A clutch is also provided as above. The threaded hole at the first end of the coupling is mate with the external thread of the valve rod bushing, and the threaded hole at the second end of the coupling is mate with the external thread of the pump rod. The sleeve contains a spinodally hardened copper-nickel-tin alloy.

In addition, various embodiments of couplings for a string of sucker rods containing a core having a first end, a central portion and a second end are described. Each of the first and second ends has an end surface. The first end has a linearly tapered part extending from the central section inward and ending at the first end surface. In other words, the first end surface has a smaller diameter than the central portion. The second end also has a linearly tapering portion extending inwardly from the central portion and ending at the second end surface. In other words, the second end surface has a smaller diameter than the central portion. Couplings are made of spinodally hardened copper-nickel-tin alloy.

These and other non-limiting features of the present invention are disclosed in more detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

The following is a brief description of the drawings, showing exemplary illustrative and non-limiting embodiments disclosed in the present invention.

In FIG. 1 shows a cross-sectional side view of an exemplary pump coupling according to the present invention, which has a linearly tapered portion at one end and a rounded lip at the other end.

In FIG. 2A is a partial cross-sectional view of a pump coupling engagement with a sucker rod and a valve rod bushing that is connected to a downhole pump.

In FIG. 2B is a side view of the coupling, sucker rod, and valve rod bushing of FIG. 2A in the assembled state.

In FIG. 3A shows an exemplary pump coupling according to the present invention which has a linearly tapered portion at both ends.

In FIG. 3B is a cross-sectional side view of the interior of the pump coupling of FIG. 3A.

In FIG. 4 is a schematic view of one embodiment of a pumping system according to the present invention.

In FIG. 5 is a graph illustrating typical values of sliding friction coefficient for various materials measured by sliding material on carbon steel. The y-axis is presented without a dimension and runs from 0 to 0.8 with an interval of 0.1. From left to right, the materials are nickel alloy, carbon steel, aluminum bronze, and copper-nickel-tin alloy.

In FIG. 6 is a graph illustrating the wear of various materials on a steel shaft. The y-axis represents the increase in clearance due to wear, in inches. The y-axis runs from 0.000 to 0.050 in 0.005 intervals. The x-axis represents the number of wear test cycles, in thousands, and runs from 0 to 180 in increments of 30. The steepest line is for hardened steel, and the flattest line is for copper-nickel-tin alloy.

In FIG. 7 shows a drawing of a pump coupling according to the present invention made of Cu-15Ni-8Sn alloy.

IMPLEMENTATION OF THE INVENTION

A more complete understanding of the components, processes and devices disclosed in this specification can be obtained from the study of the accompanying drawings. These drawings are only schematic and based on the convenience and ease of illustrating the present invention, and thus are not intended to represent the relative dimensions and dimensions of devices or components thereof and/or to define or limit the scope of exemplary embodiments.

Although certain terms are used for clarification in the following description, these terms are intended to refer only to the particular construction of the embodiments chosen to be illustrated in the drawings and are not intended to define or limit the scope of protection of the present invention. It should be understood that in the drawings and in the following description, like reference numerals refer to components with the same function.

Singular forms such as "some", "one of" and "specified" also include plural entities unless the context clearly dictates otherwise.

As used throughout the description and claims, the term "comprising" may include such variations as "consisting of" and "essentially consisting of". The terms "comprises", "include(s)", "having", "has", "may", "consists of" and their variations used in this specification are to be construed as unrestricted. transitional phrases, terms or words that require the mentioned components/steps and allow for the possibility of other components/steps. However, such a description may also be construed as disclosing formulations or processes "consisting of" and "essentially consisting of" the listed components/steps, which implies the presence of only the listed components/steps, together with any impurities that may result from them, and excludes other components/steps.

It should be understood that the numerical values used in the description and claims include numerical values that are the same when reduced to the same number of significant digits, as well as numerical values that differ from the specified value by less than the experimental error of the traditional measurement method, the type of which is disclosed in the present invention as used to determine such a value.

All ranges disclosed herein include the limit values listed and may be independently combined (eg, the range "2 grams to 10 grams" includes the limits, 2 grams and 10 grams, and all values in between).

The term "about" can be used to include any numerical value that can vary without changing the underlying function of that value. When used in relation to a range, the term "about" also discloses the range of values given by the absolute values of the two limit values; for example, "from about 2 to about 4" also discloses the range of values "from 2 to 4". The term "about" can refer to the value of plus/minus 10% of the specified number.

The present invention relates to couplings made from a spinodally hardened copper base alloy. The copper alloys of the present invention may be copper-nickel-tin alloys which have a combination of properties such as strength, ductility, high stress fracture resistance, and abrasion resistance. More specifically, the couplings are contemplated to be mechanical service couplings, sucker rod couplings, or subs used in the oil and gas industry, particularly for hydrocarbon recovery systems.

In particular, it is contemplated that the pump couplings of the present invention are intended to be used to connect a downhole pump to a sucker rod string. A typical downhole pump has a piston that reciprocates within a pump cylinder via a string of sucker rods. The piston and cylinder contain a fixed valve and a movable valve. The piston is connected to a pump drive rod or valve rod, which in turn is connected to a valve rod bushing connected to the pump rod string through a pump coupling.

A pump coupling 130 according to the present invention is shown in FIG. 1. The sucker rod coupling is used to assemble various components of the sucker rod string. For example, a pump coupling 130 may be used to connect the pump rod 210 and the valve rod bushing 220 of FIG. 3A and 3B as described below.

The pump coupling 130 itself is a core 132 having a first end 134, a central portion 170, and a second end 136, each end corresponding to a socket and having an internal thread (e.g., a socket) 138, 140 for engagement with the shaft of another component in the sucker rod string. . The core has a substantially cylindrical shape, and its length is greater than the diameter. The dotted lines 172, 174 indicate where the center section 170 connects to the first end 134 and the second end 136. The center section 170 has an outside diameter of 175.

The first end 134 has a first end surface 135. The first end 134 has a linearly tapering portion extending inward toward the end surface 135. In other words, the first end 134 is beveled. Alternatively, the first end surface 135 can be described as having a smaller diameter 144 compared to the diameter 175 of the central section 170. The term "tapered" in this case refers only to the diameter decreasing from the middle to each end, and does not require a change in diameter at any given location. In this case, the tapering portion is linear, that is, in a straight line.

The second end 136 has a second end surface 137. The second end 136 has a rounded edge 139 that merges into the end surface 137. Thus, the second end surface 137 has a diameter 146 that is smaller than the diameter 175 of the central portion 170 but larger than the diameter 144 of the first end surface 135. In specific embodiments, the diameter 146 of the second end surface is at least a quarter of an inch larger than the diameter 144 of the first end surface. In some specific embodiments, the first end face diameter 144 is 1.5/8 inches, and the second end face diameter 146 is approximately 1.9 inches, and the center portion diameter 175 is 2 inches.

The hole 142 extends through the entire core from the first end 134 to the second end 136 along the longitudinal axis 160 of the core. Both internal threads 138, 140 are on the surface of the hole. In this case, both internal threads have the same internal thread size and are mating to external threads on other components of the sucker rod string that may be connected via a coupling 130.

As further shown in the cross sectional view of FIG. 1, the pump coupling 130 includes a countersink 152, 154 on each end face 135, 137. In other words, the female thread does not extend all the way to the end face. The longitudinal axis is also indicated by line 160. The pump coupling 130 has a substantially smooth cylindrically curved outer surface 162 between the end surfaces 134, 136. In other words, the outer diameter remains constant along the length of the central section 170. The outer diameter further decreases at the tapered first end 134 and the rounded edges of the second end 136.

In FIG. 2A and FIG. 2B are side views illustrating the engagement between two components of a coupled sucker rod string according to the present invention. In FIG. 2A is an exploded partial cross-sectional view of a pump rod or stabilizer rod 210 and a valve rod bushing 220 coupled to each other via a pump coupling 130. FIG. 2A and 2B show the use of a coupling having the pump coupling geometry 130 described above and shown in FIG. one.

Sucker rod or stabilizer rod 210 has a rod body 212 and two rod ends (only rod end 214 is shown). Rod end 214 includes an externally threaded rod (or rod connector); shoulder 218, configured to abut against the end surface of the coupling; and a drive head 219 that can be engaged with a tool for tightening and screwing the stabilizer rods. The valve stem sleeve 220 has a sleeve body 222 and two sleeve ends 224, 225. The valve stem sleeve includes an externally threaded rod (or rod connector) 226 at the first end 224 of the sleeve, and a counterbore portion 227 at the second end 224 of the sleeve. Shoulder 221 is located between the two ends 224, 225 of the sleeve. The counterbore portion 227 has internal threads 228 (ie, a female connector) located on the surface of the counterbore portion for engagement with the rod of another component in the sucker rod string. A drive head 229 is also provided that can be engaged with a tool to tighten and screw in the valve stem bushing.

In FIG. 2B shows the components from FIG. 2A assembled. That is, the shaft connector of the stabilizer rod 210 is mated with the female connector at the second end of the pump coupling 130, and the shaft connector of the valve stem sleeve 220 is mated with the female connector at the first end of the sucker rod sleeve 130. In FIG. 2B shows that the outside diameter of the sleeve may be larger than the outside diameter of the components of the sucker rod string to which the sleeves are attached, such as stabilizer rod 210 and valve rod bushing 220. This prevents the connected components of the sucker rod string from contacting the production pipe (ie, conduit 411 of FIG. 4) surrounding the sucker rod string. In addition, the ends of the valve stem bushing and stabilizer bar screw into the sleeve until the sleeve abuts shoulder 218, 221.

In FIG. 3A and 3B show a further embodiment of a pump coupling 330 according to the present invention. In FIG. 3A shows a pump sleeve 330 for assembling various sucker rod string components. In FIG. 3B is a cross-sectional view of the sucker rod sleeve 330 of FIG. 3A.

In this case, the pump coupling 330 itself is a core 332 having a first end 334, a central portion 370, and a second end 336, each end corresponding to a socket and having an internal thread (i.e., a female connector) 338, 340 for engagement with the shaft of the other component in the sucker rod string. The core has a substantially cylindrical shape, and its length is greater than the diameter. The dotted lines 372, 374 indicate where the center section 370 connects to the first end 334 and the second end 336. The center section 370 has an outside diameter of 375.

The first end 334 has a first end surface 335. The first end 334 has a linearly tapering portion extending inward toward the end surface 335. In other words, the first end 334 is beveled. Alternatively, the first end surface 335 can be described as having a smaller diameter 334 compared to the diameter 375 of the central portion 370.

The second end 336 has a second end surface 337. The second end 336 also has a linearly tapering portion extending inwardly towards the end surface 337. In other words, the second end 336 is also bevelled. Alternatively, the second end surface 337 can be described as having a smaller diameter 346 compared to the diameter 375 of the central portion 370. In particular embodiments, the first end surface diameter 344 is approximately equal to the second end surface diameter 346, both of which are smaller than the diameter 375 of the central portion 370. site. In some embodiments, the first end face diameter 344 and the second end face diameter 346 are each 1 and 5/8 inches, and the center portion diameter 375 is 2 inches.

As shown in the drawings, the hole 342 extends through the entire core from the first end 334 to the second end 336 along the longitudinal axis of the core. Both internal threads 338, 340 are on the surface of the hole. In this case, both internal threads have the same internal thread size and are mating to external threads on other components of the sucker rod string that can be connected with a 330 coupling. the revision of which was released in May 2010.

As further shown in the cross sectional view of FIG. 3B, the pump coupling 330 has a countersink 352, 354 on each end face 335, 337. In other words, the female thread does not extend all the way to the end face. The longitudinal axis is also indicated by line 360. The pump coupling 330 has a substantially smooth cylindrically curved outer surface 362 along the central portion 370 of the coupling. The outer diameter further decreases at the beveled end portions 334, 336. The outer diameter of the central portion of these couplings may be larger than the outer diameter of the sucker rod string components to which the couplings are attached, such as stabilizer rods or valve rod bushings. This prevents the components of the sucker rod string from contacting the production pipe (ie, conduit 411 of FIG. 4) surrounding the sucker rod string.

In FIG. 4 shows various parts of a pumping system 400 that utilizes the various sucker rod components described above, such as pump couplings. The system 400 has a balance bar 422 that reciprocates the sucker rod string 424 containing the polished rod portion 425. The sucker rod string 224 is suspended from a balance beam to drive a downhole pump 426 located at the bottom of the well 428.

The balancer 422 is in turn driven by a connecting rod, which reciprocates under the action of a crank arm 430 driven by a power source 432 (e.g., an electric motor) connected to the crank arm 430 via a reduction gear, such as a reduction gear. . The power source may be a three-phase AC induction motor or a synchronous motor and is used to drive the pump unit. The gearbox 434 converts the engine torque into a low speed but high torque output to drive the crank arm 430. The crank arm 430 is equipped with a counterweight 436 which serves to balance the sucker rod string 424 suspended on the balance beam 422. The balancing force is also can be provided by an air cylinder, for example, similar to that found in pumping units with pneumatic shock absorbers. Belt pump units can use a counterweight moving in the opposite direction of the stroke of the rod or air cylinder to provide a balancing force.

The downhole pump 426 may be a reciprocating piston pump having a piston 438 attached to the end of the sucker rod string 424 and a pump cylinder 440 that is attached to the end of the pipeline in the well 428. The piston 438 includes a movable valve 442 and a stationary valve 444, located at the bottom of the cylinder 440. On the upward stroke of the pump, the moving valve 442 closes and lifts fluid, such as oil and/or water, over the piston 438 to the top of the well, and the fixed valve 444 opens and allows additional fluid from the reservoir flow into the pump cylinder 440. On the downstroke, mobile valve 442 opens and stationary valve 444 closes in preparation for the next cycle. The operation of the pump 426 is controlled so that the level of fluid maintained in the pump cylinder 440 is sufficient to keep the lower end of the sucker rod string 424 in fluid throughout its entire travel. The sucker rod string 424 is surrounded by conduit 411, which in turn is surrounded by casing 410. The sucker rod string 424 below the polished rod portion 425 consists of sucker rods 446 or stabilizer rods that are held together by couplings 448. The couplings 448 may be pump couplings (eg, 130, 230) and valve rod bushings (eg, 320) described above.

The connection between the sucker rod and the valve rod bushing is one of the most problematic joints in the sucker rod string. Geometric dimensions and materials of traditional sleeves lead to rapid wear of the pipeline due to contact between surfaces, as well as high speed of the fluid in the well as it exits the pump and flows through the gap between the production pipe and the sleeve between the valve rod bushing and the stabilizer rod. The use of the copper alloys described herein as the material for the couplings according to the present invention reduces the possibility of damage to threaded connections as a result of abrasion type wear between the coupling and the pipeline. In addition, the geometry (eg, beveled or rounded ends, large outside diameters) of the couplings described here prevents high energy contact between the coupling and the inner diameter of the pipeline due to misalignment. That is, conventional couplings have sharp edges that are highly likely to damage components in the event of high energy contact. In addition, the geometry of the sleeves described herein allows fluids in the well to flow into the diametral gap between the sleeve and the pipeline.

In addition, the sleeves according to the present invention, made from the copper alloys described here, are able to function as a damping device. Cushioning is provided due to the fact that the copper alloys described here have a lower modulus of elasticity than conventional materials. The cushioning allows more energy to be absorbed when the bottom surface of the valve rod bushing (eg, bushing end 325 of FIG. 3A) strikes other components of the sucker rod string as the pump piston moves down. This phenomenon reduces the propensity of the mating surface of the upper pump components to severe cold deformation during operation. Such cold forming can lead to loss of ductility and eventually to cracking, as well as the formation of "squeezed" metal protrusions extending outwardly beyond the specified diameter of these components. These protrusions destroy the inner diameter of the pipeline and the cylindrical pump housing. As a result of the destruction of these protrusions, metal fragments may occur. These fragments can cause severe damage to pump and piping surfaces as they remain in the system. Due to the high modulus of resistance of the copper alloys described herein, couplings can perform this damping function without plastic deformation. That is, the clutch is able to return to its original dimensions both after being compressed during the downward movement and after tension during the upward movement. In other words, the clutch acts as a compressed spring.

In general, the copper alloy used to make the sleeves of the present invention is cold worked before being reheated to effect spinodal degradation of the microstructure. Cold deformation is a process of mechanical change in the shape or size of a metal due to plastic deformation. This can be done by rolling, drawing, pressing, spinning, extruding, or expanding the metal or alloy. When a metal is plastically deformed, atomic dislocations occur in the material. In particular, dislocations occur across or inside metal grains. Dislocations overlap each other, while the density of dislocations in the material increases. An increase in overlapping dislocations makes it difficult for subsequent dislocations to move. This increases the hardness and tensile strength of the resulting alloy, substantially reducing the ductility and impact properties of the alloy. Cold working also improves the surface quality of the alloy. Mechanical cold forming is generally performed at a temperature below the recrystallization point of the alloy and usually takes place at room temperature.

Spinodal aging/decay is a mechanism by which different components can separate into separate regions and microstructures with different overall chemical compositions and physical properties. In particular, crystals with a total chemical composition in the central region of the phase diagram undergo exsolution. Spinodal decay on the surfaces of the alloys of the present invention results in surface hardening.

The structures of spinodal alloys consist of homogeneous two-phase mixtures formed by the separation of the initial phases at certain temperatures and compositions, which are called the region of immiscibility achieved at elevated temperature. The alloy phases spontaneously decompose into other phases for which the crystal structure remains the same, but the atoms in the structure are modified while remaining similar in size. Spinodal hardening increases the yield strength of the base metal and provides for a high degree of uniformity in composition and microstructure.

Spinodal alloys, in most cases, show an anomaly in their phase diagram, called the region of miscibility. Within a relatively narrow temperature range of the immiscibility region, atomic ordering occurs in the structure of the existing crystal lattice. The resulting two-phase structure is stable at temperatures well below the immiscibility region.

The copper-nickel-tin alloy used in the present invention essentially includes from about 9.0 wt. % to about 15.5 wt. % nickel and from about 6.0 wt. % to about 9.0 wt. % tin, with the rest being copper. This alloy can be hardened and easily converted into high yield strength products that can be used in a variety of industrial and commercial applications. This high quality alloy is designed to provide similar properties to copper-beryllium alloys.

In particular, copper-nickel-tin alloys according to the present invention contain from about 9 wt. % to about 15 wt. % nickel and from about 6 wt. % to about 9 wt. % tin, with the rest being copper. In some specific embodiments, the implementation, copper-nickel-tin alloys contain from about 14.5 wt. % to about 15.5 wt. % nickel and from about 7.5 wt. % to about 8.5 wt. % tin, with the rest being copper.

Three-component copper-nickel-tin spinodal alloys offer an advantageous combination of properties such as high strength, excellent tribological characteristics and high corrosion resistance in seawater and acidic environments. The increase in the yield strength of the base material may be associated with spinodal decomposition in copper-nickel-tin alloys.

The copper alloy may contain beryllium, nickel and/or cobalt. In some embodiments, the copper alloy contains from about 1 to about 5 wt. % beryllium and the total amount of cobalt and nickel in the range from about 0.7 wt. % to about 6 wt. %. In specific embodiments, the implementation, the alloy contains about 2 wt. % beryllium and about 0.3 wt. % cobalt and nickel. Other variants of copper alloys may contain beryllium in the range between about 5 to 7 wt. %.

In some embodiments, the copper alloy contains chromium. Chromium may be less than about 5 wt. % alloy, including from about 0.5 wt. % to about 2.0 wt. % or from about 0.6 wt. % to about 1.2 wt. % chromium.

In some embodiments, the copper alloy contains silicon. Silicon may be less than 5 wt. %, including from about 1.0 wt. % to about 3 wt. % or from about 1.5 wt. % to about 2.5 wt. % silicon.

The alloys of the present invention optionally contain small amounts of additives (eg, iron, magnesium, manganese, molybdenum, niobium, tantalum, vanadium, zirconium, and mixtures thereof). Additives may be present in amounts up to 1 wt. %, preferably up to 0.5 wt. %. In addition, small amounts of organic impurities may also be present. Small amounts of other additives such as aluminum and zinc may also be included. The presence of additional elements can affect the further increase in the strength of the resulting alloy.

In some embodiments, some magnesium is added during formation of the initial alloy to reduce the oxygen content of the alloy. This produces magnesium oxide, which can be removed from the mass of the alloy.

In particular embodiments of the present invention, the internal threads of the coupling are formed by rolling rather than cutting. It turns out that this process leads to elongation of the grains on the outer surface of the thread. Rolled threads have been found to be resistant to stripping because shear failures must occur across the grain and not in the grain. This cold forming process also provides additional strength and fatigue resistance. As a result, internal threads can have a Rockwell C hardness (HRC) of about 20 to about 40. HRC hardness can vary along the length of the thread, so this feature should not be construed as requiring all threads to have the same HRC hardness. In specific embodiments, the HRC of the thread is at least 22. The outer surface of the thread may have an HRC of at least 35.

The alloys used to make the couplings of the present invention may have a 0.2% proof yield strength of at least 75 ksi. inch, including at least 85 kilopounds per square meter. inch or at least 90 kilopounds per sq. inch or at least 95 kilopounds per sq. inch.

The alloys used to make the couplings of the present invention may have a combination of 0.2% proof yield strength and room temperature Charly V-notch fracture energy as shown in Table #1 below. These combinations are unique to the copper alloys described here. The test specimens used to make these measurements were oriented in the longitudinal direction. The values given are minimum values (ie, at least the values given), and it is preferred that the yield strength and fracture energy of the Charly V-notch specimen exceed the combinations given here. In other words, the alloys have a combination of a 0.2% proof yield strength and room temperature Charly V-notch fracture energy that is equal to or greater than the values given here.

Table No. 2 shows the properties of another exemplary copper-based alloy suitable for use according to the present invention in a sucker rod coupling or sub.

The 0.2% yield strength and tensile strength are measured in accordance with ASTM E8. Impact tests using V-notch specimens are performed in accordance with ASTM E23. Pump couplings according to the present invention can be manufactured using casting and/or molding techniques known in the art.

Couplings made from spinodally decomposable copper alloys have uniquely high tensile and fatigue strength combined with high fracture toughness, abrasion and corrosion resistance. This unique combination of properties allows couplings to meet the basic mechanical and corrosion characteristics required to reliably protect system components from abrasion damage, greatly extending system life and reducing the risk of unexpected failure. One result of this combination is an extended well life between maintenance shutdowns. In addition, by reducing friction, overall production is increased.

Some copper-nickel-tin alloys according to the present invention have a low coefficient of sliding friction. In some embodiments, the copper-nickel-tin alloy in contact with carbon steel has a sliding friction coefficient of less than 0.4. In other embodiments, the copper-nickel-tin alloy has a sliding friction coefficient of about 0.3 or less, including about 0.2 or less.

In particular embodiments of the present invention, a copper-nickel-tin alloy in contact with carbon steel typically has a sliding friction coefficient of less than 0.2 (including about 0.175 or less). By comparison, a nickel alloy in contact with carbon steel typically has a sliding friction coefficient of 0.7. Carbon steel in contact with carbon steel typically has a sliding friction coefficient of 0.6, and aluminum bronze in contact with carbon steel typically has a sliding friction coefficient of 0.4. The comparison of these values is illustrated in the graph of FIG. 5. Thus, it is possible to significantly reduce the overall friction losses in the pumping system.

Reduced friction also results in reduced pipeline wear. In FIG. 6 is a graph illustrating the use of three different bearing metals in contact with a case hardened steel shaft with an average specific bearing load of 2000 psi. inch (psi), and oscillating axial movement with side load. The y-axis indicates the change in clearance as a result of wear, with lower values referring to less wear. As can be seen, copper-nickel-tin wears less (triangles, below 0.010 inches) than aluminum bronze (squares, between 0.015 and 0.020 inches) and hardened steel (diamonds, over 0.045 inches).

Below are examples to illustrate couplings, processes and properties according to the present invention. The examples are purely illustrative and are not intended to limit the present invention to the materials, conditions, or process parameters set forth in this specification.

Examples

Example #1

Sucker rod couplings made of Cu-15Ni-8Sn alloys were used in sucker rod strings in selected exploration wells with L80 carbon steel production tubing (HRC 22-23 hardness). The mean time between failures (MTBF) for steel couplings was approximately 10 months. After installing Cu15Ni8Sn couplings, the MTBF increased by 5 times. Inspection of the Cu15Ni8Sn sleeves showed no evidence of wear or metal transfer.

One well shut down 555 days after installing Cu15Ni8Sn sleeves due to a pump leak. The tubing used to form the casing was inspected. At the same time, 50% of pipes using steel sleeves had more than 30% wall losses, and 0% of pipes using Cu15Ni8Sn sleeves had more than 30% wall losses. In addition, 25% of pipes using steel sleeves had more than 30% surface chipping, and 0% of pipes using Cu15Ni8Sn sleeves had more than 30% surface chipping. It has been calculated that this can increase the MTBF of the pipeline by at least three (3) times.

Example #2

55 Cu15Ni8Sn sleeves were installed at the bottom of a 1400 ft deep well. The following information was received.

The use of a Cu15Ni8Sn sleeve resulted in a 6.4% increase in liquid production. Results for similar tests showed a 9% increase in production, with a 12% reduction in maximum load and a 21% increase in pump stroke.

Thus, it is expected that due to the use of copper-nickel-tin alloys (compared to the use of steel), an increase in pump stroke from about 3 to about 40%, or from about 6% to about 40%, or from about 6% to about 30%, or from about 3% to about 10%, or from about 6% to about 10%.

Example #3

The coupling is made of Cu15Ni8Sn alloy. The clutch is shown in Fig. 7 and has the cross section shown in FIG. 3B. The tapered sleeve has a two (2) inch outside diameter with a three-quarter inch rolled thread. The coupling is connected to the valve stem bushing and acts as a centralizer to prevent wear of the valve stem bushing near the pipeline.

It should be understood that variations of those described above, as well as other features and functions, or alternatives thereof, may be combined into many different systems and for other purposes. Various previously unknown or unforeseen alternatives, modifications, changes or improvements may subsequently be proposed by those skilled in the art, which will also fall within the scope of legal protection given by the attached claims.

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Claims (43)

1. A string of sucker rods, containing: a pump rod having an end containing a rod with an external thread; a valve stem bushing having a first end containing an externally threaded rod and a second end comprising a countersinked female thread portion, the valve stem bushing being connected to a downhole pump; and a sleeve containing a core having a first end, a Central section and a second end, and each of the first end and the second end has an end surface, and the first end is linearly tapered inwardly from the Central section to the first end surface; wherein the diameter of the first end surface is less than the diameter of the second end surface; while the sleeve is made of a spinodally hardened copper-nickel-tin alloy, which has a coefficient of sliding friction from 0.175±10% to less than 0.4 when measured on carbon steel, and a threaded hole passes through the entire core from the first end to the second end; moreover, the threaded hole at the first end of the coupling is mate with the external thread of the valve rod bushing, and the threaded hole at the second end of the coupling is mate with the external thread of the pump rod. 2. A string of sucker rods according to claim 1, wherein the second end surface has a rounded edge, or the second end tapers linearly inwardly from the central portion to the second end surface. 3. A string of sucker rods according to claim 1, wherein the outer diameter of the pump rod is greater than the outer diameter of the valve rod bushing. 4. A string of sucker rods as claimed in claim 1, wherein the outside diameter of the sleeve is greater than both the outside diameter of the sucker rod and the outside diameter of the valve rod bushing. 5. A string of sucker rods according to claim 1, wherein the first end surface is adjacent to the shoulder of the valve rod bushing. 6. A string of sucker rods according to claim 1, wherein the second end surface is adjacent to the shoulder of the sucker rod. 7. A string of sucker rods according to claim 1, wherein the alloy contains from 8 to 20 wt. % nickel and from 5 to 11 wt. % tin, with the remainder being copper, the alloy having a 0.2% yield strength of at least 75 kilopounds per square meter. inch. 8. A string of sucker rods according to claim 1, wherein the alloy contains from 14.5 wt. % to 15.5 wt. % nickel and from 7.5 wt. % to 8.5 wt. % tin, with the rest being copper. 9. The sucker rod string of claim 1, wherein the alloy has a 0.2% yield strength of at least 95 kilopounds per square meter. inch, and a Charpy V-notch fracture energy of at least 22 lbf-ft at room temperature. 10. A coupling for a sucker rod string, comprising: a core having a first end, a central portion and a second end, each of the first end and the second end having an end surface, wherein the first end tapers linearly inwardly from the central portion to the first end surface, the second end surface has a rounded edge, and the first end surface has a diameter less than the second end surface; wherein the sleeve is made of a spinodally hardened copper-nickel-tin alloy and has a sliding friction coefficient of 0.175±10% to less than 0.4 when measured against carbon steel. 11. The coupling according to claim 10, further having a threaded hole passing through the entire core from the first end to the second end. 12. Coupling according to claim 11, wherein the hole threads have a Rockwell C hardness (HRC) of 20 to 40. 13. The coupling according to claim. 10, and each of the first end and the second end also has a countersunk part. 14. Coupling according to claim 10, and the alloy contains from 8 to 20 wt. % nickel and from 5 to 11 wt. % tin, with the remainder being copper, the alloy having a 0.2% yield strength of at least 75 kilopounds per square meter. inch. 15. Coupling according to claim 10, and the alloy contains from 14.5 wt. % to 15.5 wt. % nickel and from 7.5 wt. % to 8.5 wt. % tin, with the rest being copper. 16. The coupling according to claim 10, wherein the alloy has a 0.2% yield strength of at least 85 kilopounds per square meter. inch. 17. The coupling according to claim 10, wherein the alloy has a 0.2% yield strength of at least 95 kilopounds per square meter. inch, and a Charpy V-notch fracture energy of at least 22 lbf-ft at room temperature. 18. A method for extracting fluid from a well, comprising the steps of: functionally connect the downhole pump to the engine using a string of sucker rods; and controlling the downhole pump with the sucker rod string to extract fluid from the well; wherein the downhole pump includes a valve stem bushing having a first end containing an externally threaded rod and a second end containing a countersinked internally threaded portion; moreover, there is a sleeve for the string of sucker rods, which connects the bushing of the valve rod with the string of sucker rods; wherein the coupling for the sucker rod string comprises: a core having a first end, a central portion and a second end, each of the first end and the second end having an end surface, wherein the first end tapers linearly inwardly from the central portion to the first end surface, and either (i) the second end surface has a rounded edge, or (ii) the second end linearly tapers inwardly from the central portion to the second end surface, moreover, the coupling for the string of sucker rods is made of a spinodally hardened copper-nickel-tin alloy and has a coefficient of sliding friction from 0.175±10% to less than 0.4 when measured on carbon steel. 19. The method of claim 18 wherein the mean time between failures (MTBF) of the sucker string coupling is at least four times the MTBF of an L80 carbon steel coupling. 20. Pumping system for implementing the method according to claim 18, and the pumping system contains: downhole pump; a power source for powering the downhole pump, and a string of rods located between the downhole pump and the power source, moreover, the column of rods contains: a sucker rod including an end having an externally threaded rod; a valve stem bushing including a first end having an externally threaded shank and a second end having a countersinked female thread portion, the valve stem bushing being connected to a downhole pump; and a sleeve comprising a core having a first end, a central portion and a second end, wherein each of the first end and the second end has an end surface, wherein the first end tapers linearly inwardly from the central portion to the first end surface, and either (i) the second end surface has a rounded edge, or (ii) the second end tapers linearly inwardly from the central portion to the second end surface; while the sleeve is made of a spinodally hardened copper-nickel-tin alloy, which has a coefficient of sliding friction from 0.175±10% to less than 0.4 when measured on carbon steel, and a threaded hole passes through the entire core from the first end to the second end; moreover, the threaded hole at the first end of the coupling is mate with the external thread of the valve stem bushing, and the threaded hole at the second end of the coupling is mate with the external thread of the stabilizer rod.

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